SQL Call Stored Procedure for each Row without using a cursor

Question

Generally speaking I always look for a set based approach (sometimes at the expense of changing the schema).

However, this snippet does have its place..

-- Declare & init (2008 syntax)
DECLARE @CustomerID INT = 0

-- Iterate over all customers
WHILE (1 = 1) 
BEGIN  

  -- Get next customerId
  SELECT TOP 1 @CustomerID = CustomerID
  FROM Sales.Customer
  WHERE CustomerID > @CustomerId 
  ORDER BY CustomerID

  -- Exit loop if no more customers
  IF @@ROWCOUNT = 0 BREAK;

  -- call your sproc
  EXEC dbo.YOURSPROC @CustomerId

END

You could do something like this: order your table by e.g. CustomerID (using the AdventureWorks Sales.Customer sample table), and iterate over those customers using a WHILE loop:

-- define the last customer ID handled
DECLARE @LastCustomerID INT
SET @LastCustomerID = 0

-- define the customer ID to be handled now
DECLARE @CustomerIDToHandle INT

-- select the next customer to handle    
SELECT TOP 1 @CustomerIDToHandle = CustomerID
FROM Sales.Customer
WHERE CustomerID > @LastCustomerID
ORDER BY CustomerID

-- as long as we have customers......    
WHILE @CustomerIDToHandle IS NOT NULL
BEGIN
    -- call your sproc

    -- set the last customer handled to the one we just handled
    SET @LastCustomerID = @CustomerIDToHandle
    SET @CustomerIDToHandle = NULL

    -- select the next customer to handle    
    SELECT TOP 1 @CustomerIDToHandle = CustomerID
    FROM Sales.Customer
    WHERE CustomerID > @LastCustomerID
    ORDER BY CustomerID
END

That should work with any table as long as you can define some kind of an ORDER BY on some column.

DECLARE @SQL varchar(max)=''

-- MyTable has fields fld1 & fld2

Select @SQL = @SQL + 'exec myproc ' + convert(varchar(10),fld1) + ',' 
                   + convert(varchar(10),fld2) + ';'
From MyTable

EXEC (@SQL)

Ok, so I would never put such code into production, but it does satisfy your requirements.

I'd use the accepted answer, but another possibility is to use a table variable to hold a numbered set of values (in this case just the ID field of a table) and loop through those by Row Number with a JOIN to the table to retrieve whatever you need for the action within the loop.

DECLARE @RowCnt int; SET @RowCnt = 0 -- Loop Counter

-- Use a table variable to hold numbered rows containg MyTable's ID values
DECLARE @tblLoop TABLE (RowNum int IDENTITY (1, 1) Primary key NOT NULL,
     ID INT )
INSERT INTO @tblLoop (ID)  SELECT ID FROM MyTable

  -- Vars to use within the loop
  DECLARE @Code NVarChar(10); DECLARE @Name NVarChar(100);

WHILE @RowCnt < (SELECT COUNT(RowNum) FROM @tblLoop)
BEGIN
    SET @RowCnt = @RowCnt + 1
    -- Do what you want here with the data stored in tblLoop for the given RowNum
    SELECT @Code=Code, @Name=LongName
      FROM MyTable INNER JOIN @tblLoop tL on MyTable.ID=tL.ID
      WHERE tl.RowNum=@RowCnt
    PRINT Convert(NVarChar(10),@RowCnt) +' '+ @Code +' '+ @Name
END

Marc's answer is good (I'd comment on it if I could work out how to!)
Just thought I'd point out that it may be better to change the loop so the SELECT only exists once (in a real case where I needed to do this, the SELECT was quite complex, and writing it twice was a risky maintenance issue).

-- define the last customer ID handled
DECLARE @LastCustomerID INT
SET @LastCustomerID = 0
-- define the customer ID to be handled now
DECLARE @CustomerIDToHandle INT
SET @CustomerIDToHandle = 1

-- as long as we have customers......    
WHILE @LastCustomerID <> @CustomerIDToHandle
BEGIN  
  SET @LastCustomerId = @CustomerIDToHandle
  -- select the next customer to handle    
  SELECT TOP 1 @CustomerIDToHandle = CustomerID
  FROM Sales.Customer
  WHERE CustomerID > @LastCustomerId 
  ORDER BY CustomerID

  IF @CustomerIDToHandle <> @LastCustomerID
  BEGIN
      -- call your sproc
  END

END

If you can turn the stored procedure into a function that returns a table, then you can use cross-apply.

For example, say you have a table of customers, and you want to compute the sum of their orders, you would create a function that took a CustomerID and returned the sum.

And you could do this:

SELECT CustomerID, CustomerSum.Total

FROM Customers
CROSS APPLY ufn_ComputeCustomerTotal(Customers.CustomerID) AS CustomerSum

Where the function would look like:

CREATE FUNCTION ComputeCustomerTotal
(
    @CustomerID INT
)
RETURNS TABLE
AS
RETURN
(
    SELECT SUM(CustomerOrder.Amount) AS Total FROM CustomerOrder WHERE CustomerID = @CustomerID
)

Obviously, the example above could be done without a user defined function in a single query.

The drawback is that functions are very limited - many of the features of a stored procedure are not available in a user-defined function, and converting a stored procedure to a function does not always work.

For SQL Server 2005 onwards, you can do this with CROSS APPLY and a table-valued function.

• Using CROSS APPLY in SQL Server 2005

Just for clarity, I'm referring to those cases where the stored procedure can be converted into a table valued function.